1. Field of the Invention:
The invention described herein is an improved method to provide roof support for mining operations.
2. Description of the Prior Art:
Various methods have been suggested in the past to provide roof support for areas to be subsequently mined out. In the U.S. Pat. No. 3,527,500 to C. R. Thompson boreholes are drilled from the surface to the areas to be mine and then filled with a solidifying material. Steel rods may also be placed in this material to give added strength before the material solidifies into a pillar type support. Another method, more closely analogous to the present invention, is described in the U.S. Pat. No. 1,630,589 to W. P. Taber. This latter reference discloses horizontal roof supports being inserted before excavation takes place. To do this holes are bored or drilled at or near the top of the mineral vein and beams are inserted in each hole. Supports like the mineral to be mined out can be used and/or a reclaimable posts may be used to vertically hold the inserted beams in place.
Both of these prior art method of support differ substantially from my invention. Thompson is concerned with drilling vertically holes from the earth's surface to form underground pillar supports that have steel supporting rods. My invention is concerned with generally horizontal roof supports totally underground that have prestressed rods bonded in the roof holes. As such the drilling required is not determined or limited by the distance beneath the earth's surface mining operation are to take place. Taber does not drill from one subterranean cavity to another or use prestress rods as self supporting roof supports but depends on vertical supports, whether artificial or the material to be mined, as the method to hold the embedded horizontal roof supports. This would not only result in more obstacles in the mine to be avoided by workers and equipment but also would not allow the recovery of the total amount of material possible when the vertical supports of Taber are the material to be mined. More important, it would require miners to be in the area before mining operations take place to set up the artificial vertical supports, whereas, in my invention the roof supports are inserted weeks or even months before the miners are actually working beneath a supported roof. This advantage prevents many of the minor roof falls from occurring and thus eliminates or reduces one of the major causes of death and injury in mines. These and other advantages of my invention over the prior art will become more apparent as the following description of the invention is read.